Reciprocity, Sanctions, and the Development of Mutual Obligation in Egalitarian Societies

Discrete agent simulation was used to study several models of reciprocity and sanctions in a model egalitarian society. We found that mutual obligation between agents was maximized for indiscriminant sharing, the same condition that has been observed in several traditional cultures. Alternate sharing strategies, including ones based on kinship or sharing with those who share in return, reduced mutual obligation. When theft and sanctions were introduced into the simulations, we found that mutual obligation was maximized when individual norms were strong, i.e. when there was little tolerance to theft. Collective sanctions, represented by the ostracism of non-normative agents, produced levels of mutual obligation comparable to the case of strong individual norms, but with significant risk of population collapse. The probability of long term survival was highest when tolerance to transgressions was either very low or very high and we propose that this may be one reason for the similarity of normative systems across diverse egalitarian cultures.